The present invention relates to methods of planting sugarcane seed to achieve a high density of sugarcane plants per unit area.
Sugarcane belongs to the family of tufted grasses. Sugarcane is propagated by planting whole sugarcane stalks or cuttings of the sugarcane stalk including one or more buds. These cuttings are sometimes referred to as seed pieces or billets. Commercial sugarcane planting involves the planting, either by hand or mechanically, of whole sugarcane stalks or seed pieces. Sugarcane is planted in regularly spaced rows of xe2x80x9cVxe2x80x9d or xe2x80x9cUxe2x80x9d shaped furrows, in raised seedbeds, or on flat ground. Raised seedbeds are typically used in swampy, wet areas to keep the sugarcane seed above the level of the water table, while furrows are typically used in drier areas where irrigation may be necessary.
A typical sugarcane field planted using prior methods is illustrated in FIG. 1. In most highly mechanized farms, row spacing (20) is typically in the range of 1.4 to 2.0 meters (4.6 to 6.6 feet) between rows (21). For example, in Florida, the current commercial practice is hand planting of whole stalks in furrows spaced on approximately 1.5 meter (5 foot) centers. Once laid in the furrow, the stalks may be left whole or they may be subsequently chopped into stalk pieces of varying length. In other sugarcane growing regions, the commercial practice is to plant rows of sugarcane seed pieces with a row spacing ranging from 0.5 meters to 2.0 meters (1.6 feet to 6.6 feet) either in furrows, on flat ground or on raised beds. In each case, the distance between rows is required to permit mechanization of the sugarcane planting, cultivation and harvesting operations by providing space for equipment or laborers to travel through the sugarcane field.
Where furrows are used in the rows, the widths of the furrows are typically up to about 0.45 meters (1.5 feet) and the depths of the furrows can vary from about 2.5 centimeters to about 45 centimeters (1 inch to 18 inches) depending upon soil conditions. Where raised seedbeds are used, the height of the raised bed is typically between about 2.5 centimeters to about 45 centimeters (1 inch to 18 inches) depending upon soil conditions. Seeding rates vary depending upon the soil and climate conditions. Typically, seed pieces are placed in the furrow or in the seedbed at seed rates of between approximately 2-13.6 metric tons/hectacre with a single line or multiple lines of sugarcane seed in the furrow. Seed rates may be higher when mechanical planting equipment is used to compensate for seed damage caused by the equipment. As shown in FIG. 2, the orientation of the seed pieces (22) in the furrow has heretofore been intended to be primarily parallel to the direction of the furrow. Thus, the prior practice has been to intentionally orient the seed pieces in a direction parallel to the direction of the furrow.
In established natural stands of wild sugarcane, stalks of sugarcane may grow as close as 2 to 5 centimeters (0.75 to 2 inches) apart. In commercial plantings, however, the spacing between rows of sugarcane results in fewer plants per unit of field area, which results in less ground cover and less absorption of available light, water and nutrients during early growth stages. It has been reported that sugarcane crops grown at 1.5 meter (5.0 foot) row spacing intercept less than 60% of the available solar radiation. (Muchow et al. 1994, Radiation interception and biomass accumulation in a sugarcane crop grown under irrigated tropical conditions; Aust. J. Agric. Res. 45:37-49). Accordingly, the yield of sugarcane per unit area is reduced as a result of the spacing of rows in commercial planting. There is a large body of data indicating that decreased row spacing increases sugarcane yield. While decreased row spacing can increase sugarcane yield, narrow row spacing can be more difficult to manage and requires expensive modification of equipment.
One approach to addressing the disadvantages of traditional commercial sugarcane planting while increasing the yield of sugarcane per unit area is the use of High Density Planting (HDP). Increased planting density can significantly improve the yield per unit area from a sugarcane crop. HDP generates a more rapid ground cover than the traditional crop grown with a 1.5 meter (5.0 foot) row spacing, thereby increasing solar radiation interception and absorption of water and nutrients. In various studies, increased plant density has translated into increased numbers of sugarcane stalks per unit area, and increased stalk number is directly correlated to increased yield.
Several HDP methods have been investigated to increase sugarcane stalk density per unit area. Attempts to increase stalk population by increasing the amount of seed planted in the traditional furrow have been variable and largely unsuccessful. The use of dual rows planted close enough together so as to be able to use conventional harvest equipment has also been tested, but yield increases using this system have been variable and non-significant in many cases. As a result, the dual row planting system has not been widely adopted. (Bull et al. 2000, High density planting as an economic production strategy: (a) Overview and potential benefits; Proc. Aust. Soc. of Sugar Cane Tech. 22:9-15). In all of these methods, however, the seed pieces are placed in the furrows or seedbeds in the traditional manner, that is oriented in the direction parallel to the direction of the furrow or seedbed.
Another HDP planting method previously investigated involves the use of closely spaced rows. (Bull et al. 2000, High density planting as an economic production strategy: (b) Theory and trial results; Proc. Aust. Soc. of Sugar Cane Tech. 22:104-112). As shown in FIG. 3, the closely spaced rows (32), as proposed in the prior art, are grouped in clusters of three or four furrows. The space between rows (30) is typically 0.5 meters (1.6 feet). The distance between the centers of each group of rows (31) is typically 2.1 meters (6.7 feet). The spacing between groups of rows is established sufficiently wide to permit driving machinery between the groups of rows. As shown in FIG. 4, in these prior art close row HDP systems, the seed pieces (33) are planted in each furrow in the traditional manner with an orientation primarily parallel to the direction of the furrow.
Although the close row HDP systems can increase sugarcane yield per unit area, the close row HDP systems used to date have several drawbacks and disadvantages. Close row HDP planting relies on precision equipment and accurate seed placement to plant three or, more typically, four rows 0.5 meters apart. The close spacing of the furrows makes it difficult to prepare the furrows, as disturbed soil from one furrow can fall into the adjacent furrow. Accurate formation of the furrows is considered essential to proper germination of the sugarcane seed. The closeness of the rows makes it necessary to use specialized equipment to minimize the disturbance of the soil. Accurate placement of seed pieces is also considered essential to maintain the optimal plant population. In addition to requiring high levels of precision to form the furrows and plant the four row beds, the planters used to date for the close row HDP system are slow and labor intensive, requiring several people to feed whole stalks to the planter.
Accordingly, it is an object of the present invention to overcome one or more of the drawbacks or disadvantages of the prior art and provide methods for planting sugarcane that can achieve high densities of sugarcane plants per unit area without the need for precision soil preparation or intensive labor.
The present invention provides methods for planting sugarcane seed that can achieve high densities of sugarcane plants per unit area without the need for precision soil preparation or intensive labor. The method comprises providing sugarcane seed pieces in appropriate lengths, preparing the soil to receive the sugarcane seed pieces, placing the sugarcane seed pieces onto the prepared soil in either a random orientation to form a layer of seed pieces or in a direction perpendicular to the direction of the furrow or seedbed, and covering the sugarcane seed pieces with soil. Soil preparation is achieved either by creating rows of wide furrows or by preparing similarly wide rows of raised or flat seedbeds. The seed pieces may be placed randomly in the furrows or seedbeds, with no effort made to orient the seed pieces in a particular direction. Alternatively, the seed pieces may be oriented primarily perpendicularly to the direction of the furrows or seedbeds. In either case, the planting is performed in a manner that will result in a grid of closely spaced sugarcane plants in the furrow or seedbed. A sufficient quantity of seed pieces are placed in the furrow or in the seedbed to achieve the desired plant density.
Among the advantages of the methods of the present invention is that soil preparation does not require specialized, precision equipment. Because a single wide row is used, accuracy is not required in the formation of the furrow or seedbed. Accordingly, the time and expense involved in preparing the soil is reduced.
A further advantage of the methods of the present invention is that a high density of sugarcane stalks per unit area can be achieved, thereby increasing the yield of sugarcane per unit area.